An 87-year-old Hamilton County woman has tested positive for infection with the West Nile virus - the county's first case of the year, according to the Hamilton County General Health District.

The woman, who lives in the Loveland-Symmes Township area, had suffered a case of encephalitis, an inflammation of the brain that is one of the most severe illnesses that can be triggered by the mosquito-borne virus.

The woman remained hospitalized Wednesday, but officials, citing the new federal medical records privacy law, would not reveal her name, her condition or further details.

The case serves as a reminder that while summer is over, mosquito season continues until the first killing frost, which usually hits around Halloween, said Tim Ingram, Hamilton County health commissioner.

"We'd like to think people are doing what we've been asking them to do. But people need to remain vigilant. Older people, especially, remain at highest risk from this disease," Ingram said.

Today, county health officials plan to search in a half-mile radius around the woman's home for stagnant water that could serve as mosquito breeding sites. Water sites that cannot be emptied or drained will be treated with larvacide, Ingram said.

So far this year, West Nile virus has caused many fewer infections than last year. Last year, Ohio had 441 probable human cases and 31 deaths. This year, Ohio has 22 probable human cases and two deaths, according to the federal Centers for Disease Control and Prevention.

In Hamilton County, nine probable human cases had been reported by this time last year - of 24 total cases for the year. So even though the number of cases appears to be down, health officials are urging people to continue protecting themselves because most of last year's West Nile virus infections occurred late in the season.